Pipes used, for example, in oilfield pipelines, have been joined end-to-end to transport oil or other fluids from place to place. Often, pipelines have been joined by such methods as threading, welding, bolting, and the like. However, problems have developed with each of these pipe joining methods. For example, threaded connections loosen, leading to leaking of fluids from the joints. Connections made by welding, or bolted flanges, are labor intensive to install, and can be costly to manufacture.
To solve some of these problems, alternative solutions have been proposed. For example, a tubular coupling member can be employed to accept the ends of adjacent pipe sections. If the inner diameter of the tubular coupling member is slightly smaller than the outer diameter of the pipes, and the pipes are forced into the coupling, an interference fit is created that is secure and can be resistant to leakage. For example, such a coupling is disclosed in U.S. Pat. No. 5,709,417, the disclosure of which is incorporated herein by reference. This coupling, however, can be improved. For example, certain aspects of the interior profile of this coupling can be susceptible to stress concentrations, which create a need for thicker coupling walls to ensure adequate coupling strength.
In addition, there are known methods of making up coupling/pipe assemblies such as those discussed above. For example, one method is to use a joining machine such as that disclosed in U.S. Pat. No. 4,328,608, the disclosure of which is hereby incorporated herein by reference. Such a device grips the coupling and the pipe, and uses hydraulic force to push the pipe into the coupling. Despite the ability of such a machine to help make up the coupling/pipe assemblies, however, further improvements can be made. For example, greater precision and more reliable joints can be made up by closer monitoring of operational parameters while the pipe joints are assembled.